For example, an eccentric screw pump which comprises a conical rotor which runs in a conically designed stator, is known from U.S. Pat. No. 2,957,427. With this arrangement, it is possible to set the fit and the pressing force between the rotor and stator by way of axially displacing the rotor relative to the stator.
An adequate pressing force between the stator and the rotor is important, in order to ensure the sealedness of the pump at high pressures. Simultaneously, the fit should not be too tight, in order to keep the friction in the pump at low levels.